The following discussion of the background of the invention is merely provided to aid the reader in understanding the invention and is not admitted to describe or constitute prior art to the present invention.
Autologous adoptive cell transfer involves the collection, modification and return of a patient's immune cells, offering a promising immunotherapeutic approach for the treatment of different types of cancers. Typically, leukocytes are isolated, usually by well-established density barrier centrifugation, and T lymphocytes are expanded ex vivo using cell culture methods, often relying on the immunomodulatory action of interleukin-2. Once expanded, the cells are administered intravenously to the patent in an activated state. Such cells are referred to as effector T cells. In addition, a combination of anti-CD3 and anti-CD28 antibodies are commonly used as a surrogate for antigen presentation with appropriate co-stimmulation cues to promote the proliferation of T cells in culture. Research into interleukin-21 suggests it may also play an important role in enhancing the efficacy of T cell based therapies prepared in this manner. Other interleukins can also be used in these cultures, with an overall objective of enhancing the cytolytic function of the exampanded T lymphocytes, once re-infused into the autologous subject.
For T cells, engagement of the CD4+ and CD8+ T cell receptor (TCR) alone is not sufficient to induce persistent activation of resting naive or memory T cells. Fully functional, productive T cell activation requires a second co-stimulatory signal from a competent antigen-presenting cell (APC). Co-stimulation is achieved naturally by the interaction of the co-stimulatory cell surface receptor on T cells, known as CD28, with the appropriate counter-receptors on the surface of the APC, known as CD80 and CD86. An APC is normally a cell of host origin which displays a moiety which will cause the stimulation of an immune response. APCs include monocyte/macrophages, dendritic cells (DCs), B cells, and any number of virally-infected or tumor cells which express a protein on their surface recognized by T cells, and can also be used for the antigen-dependent activation of T cells. To induce functional activation rather than toleragenic T cells, APCs must also express on their surface a co-stimulatory molecule. Such APCs are capable of stimulating T cell proliferation, inducing cytokine production, and acting as targets for cytolytic T lympohocytes (CTL) upon direct interaction with the T cell. Several receptors that have been reported to provide co-stimulation for T-cell activation, including CD28, OX40, CD27, CD2, CD5, ICAM-1, LFA-1 (CD11a/CD18), and 4-1BB. The signaling pathways utilized by these co-stimulatory molecules share the common property of acting in synergy with the primary T cell receptor activation signal. These costimmulatory cues for T cell activation are alternatively referred to as Signal 2 and/or Signal 3; Signal 1 is presentation by APCs of epitopes on MHC class I or MHC class II restriction elements.
Recently, T cells have been genetically engineered to produce artificial T cell receptors on their surface called chimeric antigen receptors, or CARs. CARs are proteins that allow T cells to recognize a specific, pre-selected protein, or antigen, found on targeted tumor cells. CAR-T cells can be cultured and expanded in the laboratory, then re-infused to patients in a similar manner to that described above for adoptive transfer of native T cells. Through the guidance of the engineered T cell receptor, CAR-T cells recognize and destroy the cancer cells that display the specific antigen on their surfaces. In 2014, the first chimeric antigen receptor T (CAR-T) cell-based immunotherapy, known as CTL019, received breakthrough drug designation from the US Food and Drug Administration for the treatment of relapsed and refractive acute lymphoblastic leukemia (ALL).
Cytokine-associated toxicity, also referred to as a “cytokine storm” or more recently as cytokine release syndrome (CRS), is a common and potentially lethal complication of CAR-T cell therapy. CRS is a non-antigen specific toxicity that can occur as a result of the high-levels of CAR-T cell expansion and immune activation typically required to mediate clinical benefit using modern immunotherapies such as CAR-T cell transfer. Timing of symptom onset and CRS severity depends on the inducing agent and the magnitude of immune cell activation. Symptom onset typically occurs days to occasionally weeks after T cell infusion, coinciding with maximal in vivo T-cell expansion. In recent reports of CRS following adoptive T-cell therapy for cancer, the incidence and severity of the syndrome is greater when patients have large tumor burdens, due to the expression of production of proinflammatory cytokines such as TNF-α by the adoptively transferred expanding and activated CAR-T cell populations. CRS associated with adoptive T-cell therapies has been consistently associated with elevated IFNγ, IL-6, and TNFa levels, and increases in IL-2, granulocyte macrophage-colony-stimulating factor (GM-CSF), IL-10, IL-8, IL-5, and fracktalkine have also been reported.
There remains a need in the art to provide improved methods and compositions for CAR-T cell therapies, particularly for the safety of these novel medical interventions.